Hi, Dora. Try going to your User Control Panel ("User CP" in the upper-left); find "Edit Options" in the menu on the left; find "Default Thread Age Cut Off" in the center section of the settings. By default it's set to...er, uh..."Forum Default." Adjust accordingly. There's no granular step between "last year" and "all," so experiment a bit.

Oh, and you may want to also adjust the option for the order in which the message threads are displayed. If you want to move to displaying "all" or "last year," you may also want to make sure that the newest threads are shown first so that recent stuff doesn't get buried down the page.